A tooth is a calcified structure that includes a crown portion connected to one or more relatively long root portions which extend through the gum and into the jawbone. The roots of a tooth usually curve slightly as they extend away from the tooth crown to culminate in a relatively thin apex. Each tooth root includes a root canal with rough-surfaced inner walls. In a healthy tooth, the pulp chamber and root canal are filled with pulp, which includes the tooth blood supply and nerve. Dental problems which involve the tooth roots, particularly the root canals, are quite common.
When a tooth becomes diseased or damaged as a result of infection, abscess formation, periodontal disease; trauma to the tooth or a deep cavity, removal of the tooth's pulp may be the only way to save the tooth. The damaged or diseased pulp, which contains the nerves and blood supply for the tooth, can cause additional damage or infect surrounding tissues unless the tooth is treated to remove the affected pulp. Treatment of the tooth involves making an opening in the the crown of the tooth to allow access to the pulp in the tooth pulp chamber and root. The pulp is removed, and the canal and pulp chamber cleaned thoroughly and medicated, if required, to prevent further infection. Once all infection is gone, the root canal and pulp chamber are filled and sealed, and the crown of the tooth is restored. The extent of the crown restoration necessary may vary from a simple "filing" if the tooth is structurally sound to a full crown replacement supported by one or more posts placed in the root canal.
The root canal treatment preferred by endodontists involves filling the root canal and pulp chamber with an inert biocompatible material to prevent further complications. Unless the pulp is removed and the root canal refilled with a biocompatible, inert material, the damaged pulp could serve as a medium for bacteria or act as a "foreign body," and the root could become further inflamed or infected. It is especially important to insure that the root apex is sealed and filled properly to prevent the intrusion of fluids from the tissue surrounding the root into the canal, or to prevent the extrusion of filler material into this tissue.
When problems with the tooth root and the root canal arise, there may be damage to the crown of the tooth as well. Crown damage could also occur during drilling of the tooth to treat the root canal if the structural integrity of the tooth has been affected by the disease, trauma or infection that originally caused the root canal problem. To restore the crown may require the placement of one or more posts within the tooth that extend into the root canal, to anchor a crown or other restorative work. Such posts are used not only to assist in the total restoration and rehabilitation of the tooth. but are sometimes placed in the root canal as an additional tooth support, even when crown restoration is not required. Posts that are located in the root canal are typically cemented in place after the pulp is removed before the root canal is filled. Consequently, their removal can be difficult.
In some cases, additional treatment or restorative work must be performed on the tooth some time after the root canal has been filled and sealed. This may require the removal of the root canal filling to allow the necessary treatment or restoration of the tooth. Until now, root canal fillings could only be removed with considerable manipulation of the root canal and tooth. These procedures and the use of potentially toxic substances, such as chloroform, increase the attendant risk of damage to surrounding tissues resulting from available root canal treatments.
Various and diverse devices and methods have been used to fill and repair root canals. Filler points or cones made from gutta percha or silver, posts screwed into the jawbone, and obturators, such as those marketed under the name THERMAFIL by Tulsa Dental Products, have been used to fill the apical portion of the root canal. Pastes and injectable gutta percha have been used both in conjunction with the above devices and separately to fill root canals. However, all of these devices and methods have inherent disadvantages. are biocompatible, pure gutta percha points are overly flexible and lack rigidity, which causes them to bind in the root canal during insertion. Consequently, a gutta percha point often cannot be inserted as far into the root canal as it should go. In addition, it is possible to insert such a point farther into the root canal than is desirable. If this occurs, a pure gutta percha point is extremely difficult to retrieve and remove. Other available pliable biocompatible materials, such as injectable gutta percha and pastes, are difficult to control at the root apex and may be forced through the root apex. In addition, the injectable pastes sometimes tend to resorb.
Kinsman U.S. Pat. No. 674,419 and Miller U.S. Pat. No. 1,463,963 are representative of early solutions to the problem of filling a root canal. These patents disclose the use of gutta percha points having metallic cores for this purpose. Although these fillers have more rigidity and may be somewhat easier to control than pure gutta percha points, the metallic core points described in these patents are difficult to retrieve if pushed too far into the root canal. If the canal requires retreatment at a later date, moreover, this type of gutta percha metal point is very difficult to remove.
Some rigid metallic fillers, for example silver points, tend to corrode over time, as they are not highly biocompatible with root canal environment. These elongated point devices, moreover, are not flexible and cannot adequately conform to the curvature of the tooth root canal to fill and seal the canal effectively. Also, it may be difficult to place a post in the same canal with a silver point or cone. If the pulp is replaced with a silver point which extends substantially the entire length of the canal, the incisal or occlusal end of the point must be removed to accommodate a post. Removal is usually accomplished by drilling. However, not only is it difficult to drill through the silver, but such drilling vibrates the silver point so that damage to the apical seal is extremely likely. Consequently. It is necessary to notch the silver point prior to insertion in the canal so that the top of the point may be broken off with dental pliers rather than drilled. Finally, the retrieval and removal of these points for subsequent treatment of the tooth is not easily accomplished.
One recently proposed root canal filler device is a one piece endodontic obturator which includes a calibrated stainless steel carrier shaped like a standard endodontic file and coated on one end with alpha gutta percha. This carrier is provided in a range of different sizes corresponding to standard endodontic file sizes. A handle on one end of the carrier assists the dentist in the insertion of this obturator into the root canal. An endodontic file must first be inserted in the root canal to obtain the approximate distance the obturator must be inserted into the root canal. Once this distance is determined. A rubber stop on the carrier is positioned at the calibration on the carrier corresponding to this distance. The gutta percha portion of the obturator is then heated until it begins to expand and becomes plasticized, and the obturator is inserted into the root canal to the level indicated by the rubber stop. The stainless steel carrier provided with this device is significantly longer than required to fill the root canal. Consequently, the excess carrier shaft must be cut off and removed. This is done with a fissure but in a high speed hand piece while the shaft is in the root canal. The excess shaft, handle and stop are then removed to allow vertical condensation of the gutta percha.
While the aforementioned endodontic obturator represents an improvement over previously available root canal filler devices, it still suffers from some significant disadvantages. Because the gutta percha tip is heated prior to insertion into the root canal. it is possible to push the end of the stainless steel carrier shaft through the warmed gutta percha during insertion so that exposed metal rather than plastic gutta percha contacts the root apex. If too much force is exerted during insertion. not only could the metal be exposed, but the metal shaft could actually penetrate the root canal apex. In neither instance would an effective apical root canal seal be formed Severing the carrier shaft to the proper length with a fissure bur in a high speed hand piece after the obturator has been inserted into the root canal subjects the obturator to undesirable high speed vibrations that could vibrate the device loose and also traumatize the tooth. Cutting this carrier shaft inside the mouth is also more difficult for the dentist. In addition, this prior art endodontic obturator requires special treatment so that the root canal can accommodate both the obturator and a post, if one is required for restorative work. The stainless steel carrier shaft must be properly notched somewhat below the level of he rubber stop and handle prior to insertion and the shah broken off after insertion. Too large a notch will weaken the shaft so that it could break during insertion. while too small a notch may prevent breakage of the shaft at the proper time.
Moreover, the removal of this obturator from the root canal can only be accomplished with difficulty. If the obturator is notched and separated well down into the root canal, its removal is virtually impossible. The handle portion of the obturator is permanently removed when the carrier shaft is severed, and, therefore, cannot be reconnected to the shaft. As a result, removal of the obturator requires the application of heat or solvents to the gutta percha and instruments to the carrier shaft to extract them from the root canal. Consequently, subsequent treatment a tool canal into which such an obturator for has been inserted can be performed only after a series of steps potentially traumatizing to the root canal, tooth and surrounding tissue.
Finally, if the aforementioned obturator is inadvertently thrust past the apical foramen, it is almost impossible to pull the metal core back into the root canal without leaving the already plasticized gutta percha behind.
Another prior art root canal filler is described in Tosti U.S. Pat. No. 3,813,779 discloses a threaded post which is screwed through the tooth and into the jawbone to fill the root canal and anchor the tooth. Apart from the likelihood of unnecessary trauma to the tooth and severe complication should the procedure not be properly performed, this device is not likely to provide an effective root canal seal.
The prior art devices for filling root canals, therefore. suffer from numerous drawbacks. Often, these devices are too flexible so that positioning and repositioning them is difficult. More rigid devices are unable to adequately fill and seal the apical region of the root canal as they can not conform to the curvature of the tooth root. Many of the devices are inserted, positioned, or customized within the root canals in ways that unduly traumatize the tooth, gums, jawbone, and surrounding mouth areas. Moreover, if these devices are improperly manipulated, further trauma and complications could result. Available tools used to insert available root canal filler pins or points are not easy to use. None of the known devices and tools for filling root canals, moreover, is easy to use, permits the filler to be first attached and subsequently reattached to an inserter tool for adjustment or removal of the filler, or employs a reusable inserter.
Thus, the prior art fails to provide a root canal filler device including a single use substantially flexible filling cone or obturator that conforms to both the relatively long length and the curvature of a tooth root canal to effectively seal and fill the root canal and that can be adjusted to the proper length after radiographic confirmation of placement within the root canal, wherein the obturator is removably reattachable to a multiple use inserter tool whereby the obturator is inserted into a root canal so thai after the inserter tool has been separated from the obturator, the inserter can be easily reattached to the obturator to reposition or remove it, as required. There is a need, therefore, for such a two part root canal filler device including a single use obturator for effectively filling and sealing the root canal and a multiple use insertion tool for inserting and removing the obturator as required for the treatment and ongoing management of root canal problems.